Loans, Allowance for Loan Losses by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 12,884	$ 11,190
Charge-offs	(214)	(116)
Recoveries	14	13
Provision	400	500
Balance at end of period	13,084	11,587
Real Estate Loans [Member] | Residential [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,105	1,049
Charge-offs	0	(15)
Recoveries	0	0
Provision	(16)	43
Balance at end of period	1,089	1,077
Real Estate Loans [Member] | Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	4,115	3,867
Charge-offs	(200)	0
Recoveries	0	0
Provision	215	139
Balance at end of period	4,130	4,006
Real Estate Loans [Member] | Agricultural [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	4,264	3,143
Charge-offs	0	0
Recoveries	0	0
Provision	128	197
Balance at end of period	4,392	3,340
Real Estate Loans [Member] | Construction [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	58	23
Charge-offs	0	0
Recoveries	0	0
Provision	(26)	16
Balance at end of period	32	39
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	120	124
Charge-offs	(14)	(13)
Recoveries	11	10
Provision	7	2
Balance at end of period	124	123
Other Commercial Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,354	1,272
Charge-offs	0	(45)
Recoveries	3	3
Provision	(74)	43
Balance at end of period	1,283	1,273
Other Agricultural Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	752	492
Charge-offs	0	(43)
Recoveries	0	0
Provision	4	83
Balance at end of period	756	532
State and Political Subdivision Loans [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	762	816
Charge-offs	0	0
Recoveries	0	0
Provision	(197)	(27)
Balance at end of period	565	789
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	354	404
Charge-offs	0	0
Recoveries	0	0
Provision	359	4
Balance at end of period	$ 713	$ 408